Loudspeaker



Dec. 20, 1966 A HEPPNER 3,293,378

LOUDSPEAKER Filed June 28, 1963 INVENTOR lj'gnore @Hg mez $3 WW J QZZwQ 756.

United States Patent 3,293,378 LOUDSPEAKER Elmore A. Heppner, Round Lake, Ill., assignor to Heppner Manufacturing Co., a corporation of Illinois Filed June 28, 1963, Ser. No. 291,371 3 Claims. (Cl. 179115.5)

This invention relates to a loudspeaker and more particularly to a cap for use in enclosing the back side of the voice coil-magnet assembly of a loudspeaker.

It is a general object of the present invention to produce a new and improved loudspeaker.

It i a more specific object of the present invention to produce a loudspeaker provided with a cap positionable over the back side of a magnet-voice coil assembly, said cap having a chamber therein which may be sized to provide a back pressure of predetermined magnitude to improve the acoustical qualities of the loudspeaker.

Yet another object of the invention is to provide a cap covering the back side of the voice coil-magnet assembly of a loudspeaker with the cap being fabricated of soundabsorbing material so as to absorb or deaden back waves generated by the loudspeaker.

A further object of the present invention is to produce a cap for the back side of the voice coil-magnet assembly which serves to prevent dust from entering into the gap where the voice coil operates.

Other and further objects of the invention, will be readily apparent from the following description and drawings in which:

FIG. 1 is a side elevational view of a loudspeaker embodying the invention;

FIG. 2 is a section taken along the line 22 of FIG. 1;

FIG. 3 is a front elevational view partially broken away of the center portion of FIG. 1;

FIG. 4 is a section along line 44 of FIG. 3; and

FIG. 5 is a perspective view of the elements forming the cap.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail a specific embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawings, there is shown a loudspeaker provided with the usual basket 11 secured at its inner edge to a circular metal plate 12. A cone or diaphragm 13 is secured at its outer edges to the outer edge of the basket 11 by means of a gasket 14 and at its inner end the diaphragm is secured to a voice coil 15. The voice coil is maintained in proper centered relationship by a centering member or spider 16 (such as that shown in Knowles Patent 2,469,773) and a dust cap 17 is slecured to the apex of the cone 13 to overlie the voice cor Secured to the back side of the plate 12 is a yoke 18 carrying a magnet 19 positioned to locate the pole piece 20 thereof in an opening 21 formed in the center of the plate 12.

Up to this point, the parts of the loudspeaker thus far described are more or less conventional. In such loudspeakers it is necessary, or at least highly desirable, that the gap existing between the voice coil and the pole piece on the one hand, and between the voice coil and the edges of the opening 21 on the other hand, be maintained as free from dust and other foreign particles as possible, otherwise faulty operation of the speaker is apt to occur. In addition, it is customary, in order to improve the acoustical qualities of the loudspeaker, to provide some means for absorbing the back waves generated by the speaker and in the finer types of speakers means are provided for regulating the back pressure existing in the area behind the centering member 16. This is particularly important when the centering member 16 is made of relatively imperforate material to provide needed vi cous damping of the vibratory system.

In the case of a compression driver type sound generating transducer, the enclosed volume on the back side of the diagram has to be critically adjusted to correctly complement the loading eifects of the usual horn radiator associated with such transducers. Otherwise, unwanted resonances can occur in the radiated sound pressure and destroy the benefits expected from this transducer-horn combination.

According to the present invention there is provided a cap 25 which serves all of the functions set forth above. The cap 25 is made in two mating parts 26a and 26b with the parts being so formed as to define a chamber 27 therewithin when the parts are secured together. The cap arts 26a and 2612 are each provided with portions 260 and 26d which extend inwardly under the sides of the yoke 18 so as to lock the parts in position and suitable adhesives may =be applied to the edges of the parts 26a and 26b prior to their assembly around the yoke 18, including the application of adhesive to the terminal edge 28 of the cap so as to secure the same together and to the back side of the plate 12.

When so assembly as shown in FIG. 1, there is provided a decorative cover which competely dustproofs the moving voice coil assembly and at the same time provides an acoustical chamber 27 which can be sized to provide the correct back pressure during operation of the speaker and oscillation of the voice coil. Additionally, the cap 25 is preferably fabricated of sound-absorbing material such as, for example, polystyrene foam, and when so fabricated serves the further purpose of absorbing back sound waves generated by the speaker. With this cap, the enclosed volume and acoustic resistance of the back side can be optimized for wanted voice coil impedance and diaphragm radiation characteristics.

It will be readily apparent to those skilled in the art that a speaker constructed in accordance with the design disclosed not only will have the advantages set forth herein, but additionally the process of manufacturing speakers is greatly simplified by the elimination of certain parts such as dust rings, acoustic filling material, mounting devices, etc. Furthermore, once cemented in place, the cap prevents tinkering with the important parts of the loudspeaker which, when improperly done, often impairs or destroys the speakers fidelity.

I claim:

1. In a loudspeaker, a plate having a circular opening therein, a yoke secured to one side of the plate and bridging the opening, a magnet secured to the yoke and having a portion positioned in the opening and spaced from the sides thereof to define a gap therebetween, a voice coil positioned in the gap and secured to a diaphragm, and a preformed cap enclosing the magnet and yoke, said cap being fabricated of sound-absorbing material and having terminal edges secured to said one side of the plate.

2. The loudspeaker of claim 1 in which said cap is of polystyrene foam preformed into two mating parts, each having portions shaped to mate with the corresponding portion of the other part and to interlock with the yoke.

3. In combination with a loudspeaker having a plate provided With a circular opening therein, a magnet secured in position on one side of the plate and having a portion extending into the opening to produce an annular gap therewith and a voice coil movable in said gap, a dust cover for one side of said plate, said dust cover being preformed of polystyrene foam and being secured 4 in dustproof relationship to said side of the plate and said dust cover having a recess enclosing the magnet.

References Cited by the Examiner UNITED STATES PATENTS 3,222,753 12/1965 Heppner 179-l 17 X FOREIGN PATENTS 1,326,414 4/ 1963 France.

KATHLEEN H. CLAFFY, Primary Examiner.

FL N. CARTEN, Assistant Examiner. 

3. IN COMBINATION WITH A LOUDSPEAKER HAVING A PLATE PROVIDED WITH A CIRCULAR OPENING THEREIN, A MAGNET SECURED IN POSITION ON ONE SIDE OF THE PLATE AND HAVING A PORTION EXTENDING INTO THE OPENING TO PRODUCE AN ANNULAR GAP THEREWITH AND A VOICE COIL MOVABLE IN SAID GAP, A DUCT COVER FOR ONE SIDE OF SAID PLATE, SAID DUCT COVER BEING PERFORMED OF POLYSTYRENE FOAM AND BEING SECURED IN DUSTPROOF RELATIONSHIP TO SAID INSIDE OF THE PLATE AND SAID DUCT COVER HAVING A RECESS ENCLOSING THE MAGNET. 